Time instant reference for ultra wideband systems

ABSTRACT

Embodiments enable communicating Ultra Wideband (UWB) devices to collaborate by exchanging pulse shape information. The UWB devices use the pulse shape information to improve ranging accuracy. The improved ranging accuracy can be used in complex multipath environments where advanced estimation schemes are used to extract an arriving path for time-of-flight estimation. To determine the pulse shape information to be shared, some embodiments include determining location information of a UWB device and selecting the pulse shape information that satisfies regional aspects. The pulse shape information includes a time-zero index specific to a ranging signal that is used by UWB receivers to establish timestamps time-of-flight calculations. Some embodiments include measuring performance characteristics and selecting different pulse shape information based on the performance characteristics for improved accuracy.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.15/681,968, filed on Aug. 21, 2017, entitled, Pulse ShapingInteroperability Protocol for Ultra Wideband Systems, which claimspriority to U.S. Provisional Patent Application No. 62/528,343, filed onJul. 3, 2017, entitled Pulse Shaping Interoperability Protocol for UltraWideband Systems, both of which are incorporated herein by reference intheir entireties.

BACKGROUND Field

The described embodiments generally relate to techniques for UltraWideband (UWB) communications.

Related Art

An Ultra Wideband (UWB) system is a wireless communication systemutilizing short wireless radio pulses. Such a system may be referred toas an “Impulse Radio UWB system.” By using short pulses emitted at adesired carrier frequency, a wide portion of the wireless spectrum suchas several 100 MHz or even multiple GHz of spectrum around the carrierfrequency may be excited, and the resulting signal may be classified asa UWB signal.

SUMMARY

Embodiments enable communicating Ultra Wideband (UWB) devices tocollaborate with each other by exchanging pulse shape information thatcan be used for a future ranging exchange. The receiving UWB devices usethe pulse shape information to improve the ranging accuracy. Theimproved ranging accuracy can be used in complex multipath environmentswhere advanced estimation schemes are used to extract an arriving pathfor time-of-flight estimation. To determine pulse shape information tobe shared, some embodiments include determining location information ofa UWB device, and selecting the pulse shape information that satisfiesregional aspects. The pulse shape information includes a time-zero indexspecific to a received ranging signal that is used by UWB receivers toestablish timestamps for time-of-flight calculations. Some embodimentsinclude measuring performance characteristics and selecting differentpulse shape information.

Embodiments include a system, method, and computer program productutilizing a pulse shaping interoperability protocol for Ultra Wideband(UWB) communications. Some embodiments include receiving pulse shapeinformation from another electronic device, where the pulse shapeinformation is used in UWB communications between the electronic deviceand the another electronic device, receiving a ranging signal that usesfirst pulse shape information, and determining a distance between theelectronic device and the another electronic device based at least inpart on the pulse shape information and the ranging signal. Determiningthe distance includes calculating a time-of-flight associated with theranging signal. The pulse shape information includes a time-zero indexthat may be a sample of a main lobe of the pulse shape information(e.g., a first sample or a center sample of a main lobe of the pulseshape information.) The pulse shape information also satisfies one ormore regional aspects associated with location information of theelectronic device.

Some embodiments include determining performance characteristics of another ranging signal previously transmitted, determining additionalpulse shape information, transmitting the additional pulse shapeinformation to the other electronic device, and transmitting anotherranging signal using the additional pulse shape information to the otherelectronic device. To determine the performance characteristics, someembodiments include measuring an output of an antenna coupled to the oneor more processors, and determining that the output of the antenna doesnot satisfy threshold criteria.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate the presented disclosure and, togetherwith the description, further serve to explain the principles of thedisclosure and enable a person of skill in the relevant art(s) to makeand use the disclosure.

FIG. 1 illustrates an example system implementing a pulse shapinginteroperability protocol for Ultra Wideband (UWB) communications,according to some embodiments of the disclosure.

FIG. 2 is a block diagram that illustrates an example systemimplementing a pulse shaping interoperability protocol for UltraWideband (UWB) communications, according to some embodiments of thedisclosure.

FIG. 3 illustrates an example of a pulse shaping interoperabilityprotocol exchange for Ultra Wideband (UWB) communications, according tosome embodiments of the disclosure.

FIG. 4A graphically illustrates an example pulse shape for UltraWideband (UWB) communications, according to some embodiments of thedisclosure.

FIG. 4B illustrates an example data representation of a pulse shape forUltra Wideband (UWB) communications, according to some embodiments ofthe disclosure.

FIG. 5 illustrates an example ranging scenario utilizing time-of-flight(ToF), according to some embodiments of the disclosure.

FIG. 6 illustrates an example ranging scenario with scattered objects,according to some embodiments of the disclosure.

FIG. 7 illustrates an example ranging scenario with scattered objectsutilizing time-of-flight (ToF), according to some embodiments of thedisclosure.

FIG. 8 illustrates an example method for determining pulse shapeinformation, according to some embodiments of the disclosure.

FIG. 9 is an example computer system useful for implementing someembodiments or portion(s) thereof.

FIG. 10 illustrates ambiguities in distinguishing pulse effects frompropagation channel effects using compliant pulses.

The presented disclosure is described with reference to the accompanyingdrawings. In the drawings, generally, like reference numbers indicateidentical or functionally similar elements. Additionally, generally, theleft-most digit(s) of a reference number identifies the drawing in whichthe reference number first appears.

DETAILED DESCRIPTION

Some embodiments enable communicating Ultra Wideband (UWB) devices tocollaborate with improved ranging accuracy, especially in complexmultipath environments where advanced estimation schemes are used toextract an arriving path for time-of-flight (ToF) calculations. Forexample, when two UWB stations—station A and station B—first connect,they may exchange explicit pulse shaping information in the form of awaveform describing the pulse, p(t). So station A may signal explicittransmit pulse shape information, p_(A)(t), to station B, while stationB may signal transmit pulse shape p_(B)(t) to station A. That way, eachUWB station's receiver is aware of the other UWB station's pulse shapeinformation and can improve calculations and estimations based at leastin part on that known pulse shape information, according to someembodiments.

Precise knowledge of pulse shape information used at a station'stransmitter allows the use of receivers that isolate pulse shaping orother filtering effects from true propagation channel effects. Knowledgeof the pulse shape information also allows the use of signal processingtechniques that may be referred to as “deconvolution” techniques—methodsto look at an overall received signal (e.g., end-to-end impulse responsefrom transmitter to receiver) and factor out known artifacts such as,for example, transmitter pulse shaping including antenna effects orreceiver transfer characteristics. These signal processing techniquesallow extraction of a desired contribution of a wireless propagationchannel in the overall system response; in turn, this extraction can beused to determine a time instant of an arriving propagation path.

FIG. 1 illustrates an example system 100 implementing a pulse shapinginteroperability protocol for Ultra Wideband (UWB) communications,according to some embodiments of the disclosure. Example system 100 isprovided for the purpose of illustration only and is not limiting of thedisclosed embodiments. System 100 may include but is not limited to UWBdevices such as wireless communication devices 110, 120, vehiculartransponder device 130, entry transponder device 140, household device150, leash tag 160, and anchor nodes 170 a-170 c. Other UWBdevices—which are not shown in FIG. 1 for simplicity purposes—mayinclude other computing devices including but not limited to laptops,desktops, tablets, personal assistants, routers, monitors, televisions,printers, and appliances.

The exchange of pulse shaping information may also be used in a networktopology, where more than two UWB devices perform ranging activities.Although a star topology is shown in FIG. 1, peer-to-peer topologies arealso possible. For example, wireless communication device 110 maycommunicate with wireless communication device 120, and wirelesscommunication device 120 may also communicate with one or more otherwireless UWB communication devices (not shown).

When wireless communication device 110 is in proximity (e.g., within tenmeters, within one meter, etc.) to vehicular transponder device 130 orentry transponder device 140, UWB communications may enable acorresponding car door or entry (e.g., entry of a door to a house) to beunlocked, for example. The desired proximity can be established for theapplication. Likewise, when wireless communication device 110 is inproximity (e.g., within fifty meters, within twenty meter, within tenmeters, etc.) of household device 150, the settings of household device150 may be adjusted to preferences associated with or stored on wirelesscommunication device 110. In another example, leash tag 160 may be aremovable device attached to a pet collar or clothing of a wanderingtoddler where UWB communications between leash tag 160 and wirelesscommunication device 110 result in an alarm notification on wirelesscommunication device 110 when leash tag 160 exceeds a configurabledistance threshold from wireless communication device 110.

The above UWB devices can be portable or mobile, and can determinerelative positions and/or distances with each other. Some UWB devicesmay be stationary and together they may determine absolute positions orgeographic locations. For example, anchor nodes 170 a-170 c may betransponders in fixed locations, such as on a ceiling in a building or ashelf in a store. One or more anchor nodes 170 may be used inconjunction with wireless communication device 110 to improve theaccuracy and reliability of ranging activity. In some embodiments, thedevices may triangulate and determine a geographic location that may beused to provide local direction information (e.g., a user may obtaindirections to find a particular item in a store or supermarket that maybe presented on wireless communication device 110.)

FIG. 2 is a block diagram that illustrates an example system 200implementing a pulse shaping interoperability protocol for UWBcommunications, according to some embodiments of the disclosure. System200 may include central processing unit (CPU) 210, UWB transceiver 220,communication interface 225, communication infrastructure 230, memory235, global positioning system (GPS) 240, local detector 245, andantenna 250.

UWB transceiver 220 performs UWB transmit and receive functions, and maybe coupled to antenna 250. Communication interface 225 allows system 200to communicate with other devices that may be wired and/or wireless.Communication infrastructure 230 may be, e.g., a bus or other suchinterconnect. Memory 235 may include random access memory (RAM) and/orcache, and may include control logic (e.g., computer software) and/ordata. GPS 240 determines the location of system 200 and that informationmay be transmitted to CPU 210 so that pulse shape information may beselected to satisfy regional aspects (e.g., regional governmentregulations and laws). Antenna 250 may include one or more antennas thatmay be the same or different types. Local detector 245 may measureantenna outputs to detect, for example, that that the current pulseshape information being used is not satisfactory. The antenna outputmeasurement may be due to antenna load mismatches, impedance mismatches,and/or other antenna output behaviors that may be affected by localand/or context-specific surroundings (e.g., wireless communicationdevice 110 in a shirt pocket adjacent to a UWB audio headset). Issuesdetermined by local detector 245 may result in notification andselection of different pulse shape information for future UWBcommunications, according to some embodiments. System 200 may alsodetermine when received signal strength indicator (RSSI) levels do notsatisfy a given threshold, and thus selection of different pulse shapeinformation may be implemented for future UWB communications.

FIG. 3 illustrates an example of a pulse shaping interoperabilityprotocol exchange 300 for Ultra Wideband (UWB) communications, accordingto some embodiments of the disclosure. In some embodiments, duringconnection setup when station A 310 (e.g., wireless communication device110 of FIG. 1) and station B 320 (e.g., wireless communication device120, vehicular transponder device 130, entry transponder device 140,household device 150, leash tag 160, or anchor nodes 170 a-170 c ofFIG. 1) first connect, they may exchange pulse shape informationdescribing their desired pulse, p(t), that they choose to use for UWBcommunication. In other embodiments, pulse shape information can beexchanged at any other time prior to a ranging operation.

At 340, for example, station A 310 may transmit pulse shape informationregarding station A 310's pulse choice, p_(A)(t), to station B 320. At350, station B 320 may transmit pulse shape information regardingstation B 320's pulse choice, p_(B)(t), to station A 310. This way, eachstation's receiver may be informed of the other station's pulse shapeinformation and improve ranging estimations accordingly.

This “in-the-field” exchange of pulse shape information is beneficial ifa specific circuit implementation of station A 310 or station B 320 mayoperate using one of a variety of antenna types that can affect thepulse shape radiated by the antenna. For example, as a function of theantenna that station A 310 uses, station A 310 may signal the pulseshape information, p_(A)(t), to station B 320 so that station B 320 mayprepare for subsequent ranging events with station A 310.

The connection setup between station A 310 and station B 320—includingexchange of pulse shape indices or explicit pulse shape waveform andauxiliary information such as “time-zero” information—can take place onany (wireless or non-wireless) communication channel available betweenthe two stations. In some embodiments, the connection setup and transferof pulse shape information can take place on a Bluetooth or Wifi (e.g.,Wireless LAN) link or another narrowband system, while the rangingsignaling and estimation of the range based on the pulse shapeinformation can be carried out via an Impulse Radio UWB system. Datatransmission capabilities of the UWB link between stations A 310 and B320 may be used directly, according to some embodiments.

At 360, during a ranging operation, station A 310 may transmit a rangingsignal using pulse p_(A)(t) to station B 320. At 370, station B 320 maytransmit a ranging signal using pulse p_(B)(t) to station A 310. Inaddition, stations A 310 and/or B 320 may update pulse shape informationin the middle of ranging exchanges, e.g., to adapt to localenvironmental conditions (e.g., antenna loading). This adaptation tolocal environmental conditions is described further with respect to FIG.8 below.

In some embodiments, during connection setup or on-going rangingexchanges, a UWB station can also request a preferred pulse shape to beused by a peer device, according to some embodiments. This request maybe driven by a need to use a low-power estimator mode or to cater tochanging propagation (multipath) conditions where the preferred pulseshape may be more suitable than others.

FIG. 4A graphically illustrates an example pulse shape 400 for UltraWideband (UWB) communications, according to some embodiments of thedisclosure. FIG. 4B illustrates an example data representation of pulseshape 400 for Ultra Wideband (UWB) communications, according to someembodiments of the disclosure. The pulse shape information can beconveyed in the form of a sequence (series) of waveform samples at asuitable sampling rate. For instance, a pulse waveform spanning 10 nsmay use a description that provides a sample value every 100 ps, for atotal of 100 sample values. In FIGS. 4A and 4B, the length of samplevalues is set at 61 as reflected in the sample index of (0-60). Eachsample value may be represented digitally with a certain resolution suchas, for example, 8 bits per sample. Note that the time resolution of thepulse waveform (e.g., 100 ps or a finer or coarser time step)communicated between UWB devices may either be standardized or may besignaled along with the pulse waveform. In general, the samples may becomplex-valued (e.g., contain real and imaginary parts) to representequivalent baseband arbitrary pulse waveforms that may be emitted in apassband around a desired carrier frequency.

FIGS. 4A and 4B illustrate the concept of time-zero of a pulse. StationsA 310 and B 320 have a common notion of what they refer to as the“center” of the pulse to determine their respective time instantreferences to calculate ToF measurements. For instance, transmittingstation A 310 may use as time instant reference, the time the main peakof its pulse p_(A)(t) left the antenna. Assuming that FIGS. 4A and 4Brepresent p_(A)(t), then time-zero=index 21; meanwhile, receivingstation B 320 may expect a signal based on pulse p_(A)(t) and estimatethe arrival of p_(A)(t). Station B 320 may use a different timereference point to calculate the ToF associated with received pulsep_(A)(t) such as, for example, a center of the main peak of pulsep_(A)(t) it receives as a time reference (e.g., time-zero=index 30), a“center of gravity approach,” or other metric not targeting the largestpeak to refer to the time instant reference that station B 320 recordsas the arrival time of pulse p_(A)(t). With the different time instantreferences for p_(A)(t) used by stations A 310 and B 320, an inaccuratetime-of-flight calculation—and ultimately, poor quality UWBcommunications—can result.

Unless both stations A 310 and B 320, use a common agreed-upon pointtime-zero in pulse shape p_(A)(t), the ToF may not be unambiguouslyextracted. In some embodiments, along with the pulse shape waveform, thesample index representing time-zero, e.g., the time instant referenceused for time stamps, is communicated between UWB stations.

FIG. 4B includes data that conveys example pulse shape information ofpulse shape 400 of FIG. 4A, according to some embodiments. Theinformation may be in the form of the structured table data thatincludes the following:

-   -   number of samples: LENGTH=61;    -   time-zero sample index: TIME_ZERO=21;    -   assumed sample rate FSAMP: as an oversampling factor 20 relative        to an implied reference rate corresponding to the pulse rate of,        e.g., 499.2 MHz; and    -   individual sample values in, e.g., 8 bits representation:        SAMPLES={0, 0, 0, 1, 2, 2, 3, . . . }, which in this example        would include 61 values correlating with the number of samples.        In some embodiments, the samples may be complex-valued, so there        may be two sample sequences SAMPLES_REAL and SAMPLES_IMAG, to        represent the real and imaginary parts of the effective complex        baseband pulse representation, respectively.

The above information is exemplary and based on the disclosure herein, aperson of ordinary skill in the art will recognize that the pulse shapeinformation can include other types of information. These other types ofinformation are within the spirit and scope of the present disclosure.

In some embodiments, impulse-Radio UWB systems can be used to transmitthe pulse shape information (e.g., in digital form) between differentwireless stations. Also, due to the high bandwidth and short temporallength of the pulses, these systems lend themselves to preciselyestimate the “range” (distance) between associated UWB wireless nodes.In some embodiments, the range can be calculated based on ToFmeasurements between the time of departure of the signal at station A310 and arrival of the signal at station B 320.

Other UWB systems may include a compliance check for a pulse shape,p(t). An issue with the compliance check for the pulse shape, p(t), isthat it may be insufficient and may create interoperability problems.For example, when two different pulse shapes that each satisfies thecompliance check are transmitted from station A to station B, therespective propagated signals received at station B may be substantiallythe same. Thus, uncertainty and inaccuracy exists in determining (ordetermining an estimate of) the distance (e.g., the range) between atransmitter and a receiver.

For example, FIG. 10 illustrates ambiguities in distinguishing pulseeffects from propagation channel effects using compliant pulses. StationA 1010 may be a mobile UWB device and station B 1020 may be a mobile orstationary UWB device. When station A 1010 and station B 1020 are closetogether, compliant pulse p_(top)(t) 1025 is transmitted from station A1010 through a wireless propagation channel with two propagation paths:an arriving line of sight (LOS), PPB 1035 and a reflection PPA 1030. Thereceive signal rx_(top)(t) 1040 received at station B 1020 exhibits twopeaks. To demonstrate the ambiguity, when station A 1010 and station B1020 are farther apart than before, station A 1010 may also transmitanother compliant pulse, p_(bot)(t) 1045, that has a sidelobe—in thiscase a single sidelobe before the main lobe—to station B 1020. In thepropagation channel, there is a single LOS propagation path, PPC 1050.The corresponding receive signal, rx_(bot)(t) 1060, received at stationB1020 appears identical to the receive signal rx_(top)(t) 1040. This canpose a challenge to a receiver at station B, as the identical receivedwaveforms can be based on a range-determining propagation path PPB orPPC. Although the two scenarios differ substantially in their geometryat the transmitter, the receiver at Station B 1020 cannot distinguishbetween the top scenario (based on the LOS path, PPB 1035) wherestations A 1010 and B 1020 are closer in range than in the bottomscenario where the range determination is based on the LOS path, PPC1050, that arrives much later.

The above issues in other UWB systems, among other things, are addressedby the embodiments described herein. For example, FIG. 5 illustrates anexample ranging scenario 500 utilizing time-of-flight (ToF), accordingto some embodiments of the disclosure. As a convenience and not alimitation, FIGS. 5-8 are described with regard to elements in FIGS.1-3, 4A, and 4B to demonstrate how pulse shape information conveyedimproves the accuracy of ToF calculations and hence improves UWB deviceinteroperability in UWB communications.

Station A 510 and station B 520 are substantially the same as station A310 and station B 320 of FIG. 3, respectively. Further, transmissions525 and 560 are substantially the same as transmissions 360 and 370 ofFIG. 3, respectively.

At time, t_(A1), wireless UWB signal 525 based on p_(A)(t), leaves theantenna at station A 510. Note that t_(A1) is determined by station A510 based on station A's time-zero (e.g., FIGS. 4A and 4B pulsep_(A)(t)'s time-zero=index 21). The distance between stations A 510 andB 520, d_(AB) 580, is unknown before the ranging measurement and is thedesired quantity. At time t_(B1), wireless UWB signal 525 arrives at theantenna input of station B 520. Station B 520 determines t_(B1) based onthe time-zero index of 21 based on the pulse shape information (e.g.,FIG. 4B) that station B 320 previously received via 340 from station A310 of FIG. 3. Thus, knowing time-zero for wireless UWB signal 525 (orp_(A)(t)) is important for determining ToF and subsequently, calculatingthe distance d_(AB) 580 shown below.

ToF 530 of wireless UWB signal 525 is given by a temporal difference:

ToF=t _(B1) −t _(A1).  (Eq. 1)

Note that assuming wireless UWB signal 525 is traveling at the speed oflight c, which is an acceptable approximation in air, the range ofd_(AB) 580 can be calculated as follows:

d _(AB)=ToF/c=(t _(B1) −t _(A1))/c.  (Eq. 2)

For the range calculation in Eq. 2, ToF 530 (or, equivalently, thedifference between time instances t_(A1) and t_(B1)) needs to becalculated. In some embodiments, stations A and B operate as asynchronized system with a common clock (or time) reference, such as theglobal time (GMT or otherwise common time base) with high precision andfine resolution. In such a synchronized system, station A 510 canmeasure a time of departure of wireless UWB signal 525 at t_(A1), andstation B 520 can measure a time of arrival of wireless UWB signal 525at t_(B1) based on the common clock reference. Once both t_(A1) andt_(B1) are available, ToF 530 and range d_(AB) 580 can be calculatedusing equations (1) and (2).

In systems where stations A 510 and B 520 do not operate using a commonclock reference synchronized between these two stations, stations A 510and B 520 may have their own respective local clocks. The local clocksused to measure t_(A1) and t_(B1) in stations A 510 and B 520,respectively, can have an unknown offset with respect to each other andmay operate at different clock speeds. Thus, the ranging calculationusing equations (1) and (2), as described above, may be inaccurate.

In some embodiments, to overcome the inaccuracy with stations that havea local clock, a Two-Way-Ranging (TWR) approach may be used. In TWR,after receiving wireless UWB signal 525, station B 520 switches fromreceive mode to transmit mode. After a receive-to-transmit turnaroundtime T_(B,TO) 540, station B 520 sends a second signal wireless UWBsignal 560 to station A 510 at time t_(B2). In some embodiments, stationB 520 determines t_(B2) based on a second time-zero value associatedwith a pulse p_(B)(t) selected by station B 320. The second time-zerovalue is conveyed during a connection setup from station B 320 tostation A—see 350 of FIG. 3. Wireless UWB signal 560 arrives at stationA 510 at time t_(A2). Station A 510 determines t_(A2) based on thesecond time-zero value. Thus, the conveyance of respective time-zerovalues enables stations A 510 and B 520 to accurately determinetimestamps to determine ToF values.

A delay of wireless UWB signal 560 to travel from station B 520 tostation A 510 (across a wireless medium) can be represented by ToF 550.

The desired range d_(AB) 580 can be extracted. Station A 510 measuresthe total round-trip time T_(A,RT)=t_(A2)−t_(A1). This measurement isbased on station A 510's local clock. Station B 520 measures the time ittakes between reception of wireless UWB signal 525 and transmission ofwireless UWB signal 560, T_(B,TO)=t_(B2)−t_(B1). This measurement isbased on station B 520's local clock.

ToF 530 or ToF 550 (they are equal) can be calculated as follows:

ToF=(T _(A,RT) −T _(B,TO))/2={(t _(A2) −t _(A1))−(t _(B2) −t_(B1))}  (Eq. 3)

Thus, d_(AB) 580 may be calculated using Eq. (2) as follows:

d _(AB)ToF/c={(t _(A2) −t _(A1))−(t _(B2) −t _(B1))}/c.

The calculation of Eqs. (2) and/or (3) may be carried out by station A510, station B 520, or some other node in system 100 (not shown) that issupplied with both T_(A,RT) and T_(B,TO). If one of stations A 510 or B520 is in charge of this calculation, the respective missing quantity,T_(A,RT) or T_(B,TO), is communicated to the other station through thewireless link or another means of communication. If a differentnetworking node other than stations A or B is responsible to calculatethe ToF and range, stations A 510 and B 520 will need to relay T_(A,RT)and T_(B,TO) to the other node.

Thus, the conveyance of pulse shape information for p_(A)(t) depicted inFIG. 4A and included in FIG. 4B, as well as the pulse shape informationfor p_(B)(t) (represented at 350 of FIG. 3) especially time-zeroinformation, enables accurate calculations of the ToF.

FIG. 6 illustrates an example ranging scenario 600 with scatteredobjects, according to some embodiments of the disclosure. Station A 610and station B 620 are substantially the same as station A 310 andstation B 320 of FIG. 3, respectively. Further, transmission PP1 issubstantially the same as transmission 360 of FIG. 3.

Scenario 600 illustrates an environment with scattered objects labeledOb2, Ob3, and Ob4, that act as reflectors of a wireless UWB signaltransmitted by station A 610 to station B 620. A first anddirect/line-of-sight (LOS) propagation path is shown as PP1 andadditional propagation paths are shown as PP2, PP3, and PP4. Propagationpaths PP2-PP4 take longer to arrive at station B 620, as each effectivedistance is greater. Using an abstract, idealized model of an infinitelysharp pulse emitted by station A 610, receiver station B 620 receivesmultiple copies of the signal that arrive at different times, asillustrated in FIG. 7.

In some embodiments, ternary sequences and repetition thereof in UWBsystems can be used for a UWB system to extract various propagationpaths, along with the direct/LOS propagation path, to estimate the rangein the presence of noise and/or interference. Since the sequence ofternary pulses emitted by the transmitter at station A 610 is known tothe receiver at station B 620, the latter can use correlation andaveraging techniques to determine a channel impulse response (CIR); thatis, the line-up of propagation paths as illustrated in the example withpulses PR1, PR2, PR3, PR4 shown in FIG. 7.

FIG. 7 illustrates an example ranging scenario 700 with scatteredobjects utilizing time-of-flight (ToF), according to some embodiments ofthe disclosure. Station A 710 and station B 720 are substantially thesame as station A 610 and station B 620 of FIG. 6. Further, transmissionPT is substantially the same as transmission PP1 of FIG. 6.

The propagated transmit signal PT from station A 710 translates intofour propagated receive signals PR1, PR2, PR3, and PR4 at station B 720.The direct propagation path PP1, which is assumed to be the LOS path, isshown as PR1 and represents a LOS distance between stations A 710 and B720. Station B 720 determines the first propagation path PP1 (or PR1)from later propagation paths PR2, PR3, and PR4 to extract the ToFparameter corresponding to the range between stations A 710 and B 720.Station B 720 extracts the time instant the first propagation path isreceived at t_(B1) as discussed above so that the range between stationsA 710 and B 720 under multipath conditions may be determined.

For example, using Eqs. (1) and (2), ToF 730 may be determined asfollows:

ToF=t_(B1)−t_(A1); and subsequently, d_(AB) 680 may be determined as:

d _(AB)=ToF/c=(t _(B1) −t _(A1))/c.

Time t_(A1) represents the time that propagated transmit signal PTleaves the antenna at station A 710, as determined by station A 710based on station A 710's time-zero. Station B 720 determines time t_(B1)based on a time-zero based on the pulse shape information p_(A)(t)(e.g., FIG. 4B) that station B 320 previously received via 340 fromstation A 310 of FIG. 3. Thus, knowing time-zero for propagated transmitsignal PT (or p_(A)(t)) is important for determining ToF 730, andsubsequent calculation of the ranging distance between stations A 710and B 720. Thus, the conveyance of pulse shape information and thetime-zero information in particular enables accurate ranging andimproves interoperability among UWB devices.

FIG. 8 illustrates an example method 800 for determining pulse shapeinformation, according to some embodiments of the disclosure. Method 800may be performed by any UWB stations as described in system 100 of FIG.1 and system 200 of FIG. 2. As an example, method 800 may be performedby system 200 where CPU 210 may execute instructions stored in acomputer-readable medium of memory 235 to perform the operations ofmethod 800.

Method 800 begins at 810 where system 200 determines its location. Forexample, if a user travels to another country (e.g., Japan or France)and turns on wireless communication device 110 of FIG. 1 (also system200 of FIG. 2), GPS 240 may determine a location for system 200. CPU 210may receive location information from GPS 240 or via CPU 210, forexample.

At 820, system 200 determines, based on the determined location andregional aspects, an appropriate pulse shape information that system 200plans to use and to be shared with other UWB devices. As an example, CPU210 may determine, based on tables stored in memory 235, the pulse shapeinformation that satisfies the regional aspects such as governmentregulations, regional laws, and/or local rules.

For example, a wireless device may operate at different carrierfrequencies and in different regulatory regions (e.g., US/FCC,Europe/ETSI, etc.), and each region may have specific rules andconstraints on allowed spectral mask, power spectral density limits, orways to measure various metrics to determine compliance in the region.Therefore, a transmitter in the wireless device may need to adjust itspulse shape optimally based on the wireless device's region to maximizespectral use and performance potentials. Optimal transmitter circuitproperties may be context-dependent and dependent on the wirelessdevice's region. Once the transmitter adjusts the pulse shapeaccordingly, a ranging receiver may need to adjust its local processingto cater to the transmitters new signaling properties. Thus, asdescribed herein, the ability to exchange pulse shapes betweenassociated devices assists in maximizing system performance from regionto region.

At 830, system 200 transmits the pulse shape information to another UWBstation, during connection setup, for example. The pulse shapeinformation includes information—such as, for example, the informationdescribed above in FIG. 4B—that is transmitted via UWB transceiver 220,communication interface 225, and antenna 250. In some examples UWBtransceiver 220 is coupled directly to antenna 250.

At 840, system 200 analyzes various performance characteristicsincluding but not limited to received signal strength indicator (RSSI)and notifications from local detector 245 and determines whetherdifferent pulse shape information should be used. If system 200determines that different pulse shape information is preferable, method800 may select the appropriate pulse shape information that alsosatisfies regional aspects (e.g., at 820) and transmits the appropriatepulse shape information to UWB stations accordingly (e.g., at 830).

The embodiments discussed above describe a process or protocol withmessage exchanges between participating UWB stations. As discussedabove, pulse shape information can be exchanged between UWB stations.Such exchanges have, among others, the following benefits:

-   -   Resolves ambiguities in pulse shape definitions and thereby        facilitates successful operation of ranging estimation in dense        multipath environments.    -   Improves achievable ranging accuracy while maintaining        implementers' degree of freedom to design a circuit that best        suits design processes and hardware constraints.    -   Improves flexibility to adjust system parameters to changing        environments (hardware/platform changes, multipath environments,        etc.).    -   Improves performance for “Angle-of-Arrival” estimation in UWB        receivers utilizing multiple receive antennas.    -   Improves receive sensitivity of the data detection parts of UWB        receivers as the receiver can be optimally matched to the        transmitters waveform.    -   Improves ranging accuracy by allowing adjustment of pulse        shaping as a function of regulatory constraints, including        carrier frequency, regulatory region, and others.

Various embodiments can be implemented, for example, using one or morecomputer systems, such as computer system 900 shown in FIG. 9. Computersystem 900 can be any well-known computer capable of performing thefunctions described herein. For example, and without limitation,electronic devices such as laptops, desktops as described with regard toFIG. 1, the other node in system 100 as described with respect to FIG.5, and/or other apparatuses and/or components shown in the figures. Thelaptops and desktops or other UWB devices may include the functions asshown in system 200 of FIG. 2 and/or some or all of the functions ofsystem 900 of FIG. 9. For example, computer system 900 can be used inwireless devices to exchange pulse shape information—as describedabove—among UWB devices.

Computer system 900 includes one or more processors (also called centralprocessing units, or CPUs), such as a processor 904. Processor 904 isconnected to a communication infrastructure or bus 906. Computer system900 also includes user input/output device(s) 903, such as monitors,keyboards, pointing devices, etc., that communicate with communicationinfrastructure 906 through user input/output interface(s) 902. Computersystem 900 also includes a main or primary memory 908, such as randomaccess memory (RAM). Main memory 908 may include one or more levels ofcache. Main memory 908 has stored therein control logic (e.g., computersoftware) and/or data.

Computer system 900 may also include one or more secondary storagedevices or memory 910. Secondary memory 910 may include, for example, ahard disk drive 912 and/or a removable storage device or drive 914.Removable storage drive 914 may be a floppy disk drive, a magnetic tapedrive, a compact disk drive, an optical storage device, tape backupdevice, and/or any other storage device/drive.

Removable storage drive 914 may interact with a removable storage unit918. Removable storage unit 918 includes a computer usable or readablestorage device having stored thereon computer software (control logic)and/or data. Removable storage unit 918 may be a floppy disk, magnetictape, compact disk, DVD, optical storage disk, and/any other computerdata storage device. Removable storage drive 914 reads from and/orwrites to removable storage unit 918 in a well-known manner.

According to some embodiments, secondary memory 910 may include othermeans, instrumentalities or other approaches for allowing computerprograms and/or other instructions and/or data to be accessed bycomputer system 900. Such means, instrumentalities or other approachesmay include, for example, a removable storage unit 922 and an interface920. Examples of the removable storage unit 922 and the interface 920may include a program cartridge and cartridge interface (such as thatfound in video game devices), a removable memory chip (such as an EPROMor PROM) and associated socket, a memory stick and USB port, a memorycard and associated memory card slot, and/or any other removable storageunit and associated interface.

Computer system 900 may further include a communication or networkinterface 924. Communication interface 924 enables computer system 900to communicate and interact with any combination of remote devices,remote networks, remote entities, etc. (individually and collectivelyreferenced by reference number 928). For example, communicationinterface 924 may allow computer system 900 to communicate with remotedevices 928 over communications path 926, which may be wired and/orwireless, and which may include any combination of LANs, WANs, theInternet, etc. Control logic and/or data may be transmitted to and fromcomputer system 900 via communication path 926.

The operations in the preceding embodiments can be implemented in a widevariety of configurations and architectures. Therefore, some or all ofthe operations in the preceding embodiments may be performed inhardware, in software or both. In some embodiments, a tangible apparatusor article of manufacture comprising a tangible computer useable orreadable medium having control logic (software) stored thereon is alsoreferred to herein as a computer program product or program storagedevice. This includes, but is not limited to, computer system 900, mainmemory 908, secondary memory 910 and removable storage units 918 and922, as well as tangible articles of manufacture embodying anycombination of the foregoing. Such control logic, when executed by oneor more data processing devices (such as computer system 900), causessuch data processing devices to operate as described herein.

Based on the teachings contained in this disclosure, it will be apparentto persons skilled in the relevant art(s) how to make and useembodiments of the disclosure using data processing devices, computersystems and/or computer architectures other than that shown in FIG. 9.In particular, embodiments may operate with software, hardware, and/oroperating system implementations other than those described herein.

It is to be appreciated that the Detailed Description section, and notthe Summary and Abstract sections, is intended to be used to interpretthe claims. The Summary and Abstract sections may set forth one or morebut not all exemplary embodiments of the disclosure as contemplated bythe inventor(s), and thus, are not intended to limit the disclosure orthe appended claims in any way.

While the disclosure has been described herein with reference toexemplary embodiments for exemplary fields and applications, it shouldbe understood that the disclosure is not limited thereto. Otherembodiments and modifications thereto are possible, and are within thescope and spirit of the disclosure. For example, and without limitingthe generality of this paragraph, embodiments are not limited to thesoftware, hardware, firmware, and/or entities illustrated in the figuresand/or described herein. Further, embodiments (whether or not explicitlydescribed herein) have significant utility to fields and applicationsbeyond the examples described herein.

Embodiments have been described herein with the aid of functionalbuilding blocks illustrating the implementation of specified functionsand relationships thereof. The boundaries of these functional buildingblocks have been arbitrarily defined herein for the convenience of thedescription. Alternate boundaries can be defined as long as thespecified functions and relationships (or equivalents thereof) areappropriately performed. In addition, alternative embodiments mayperform functional blocks, steps, operations, methods, etc. usingorderings different from those described herein.

References herein to “one embodiment,” “an embodiment,” “an exampleembodiment,” or similar phrases, indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it would be within the knowledge of persons skilled in therelevant art(s) to incorporate such feature, structure, orcharacteristic into other embodiments whether or not explicitlymentioned or described herein.

The breadth and scope of the disclosure should not be limited by any ofthe above-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

What is claimed is:
 1. An electronic device comprising: a transceiver;and one or more processors communicatively coupled to the transceiverand configured to: receive via the transceiver, a time instant referencefrom an other electronic device, wherein the time instant reference isused to process Ultra Wideband (UWB) communications between theelectronic device and the other electronic device; receive via thetransceiver, a ranging signal based at least in part on the time instantreference; and determine an estimated distance between the electronicdevice and the other electronic device based at least in part on thetime instant reference and the ranging signal.
 2. The electronic deviceof claim 1, wherein the time instant reference identifies a first sampleof a main lobe of the ranging signal.
 3. The electronic device of claim1, wherein the time instant reference identifies a center sample of amain lobe of the ranging signal.
 4. The electronic device of claim 1,wherein the one or more processors are further configured to: receivepulse shape information that satisfies one or more regional aspectsassociated with a location of the electronic device.
 5. The electronicdevice of claim 1, wherein to determine the estimated distance, the oneor more processors are configured to calculate a time-of-flightassociated with the ranging signal.
 6. The electronic device of claim 1,wherein the one or more processors are further configured to: determineone or more performance characteristics of another ranging signalpreviously transmitted; determine a different time instant reference;transmit the different time instant reference to the other electronicdevice; and transmit another ranging signal using the different timeinstant reference to the other electronic device.
 7. The electronicdevice of claim 6, wherein to determine the one or more performancecharacteristics, the one or more processors are configured to: measurean output of an antenna communicatively coupled to the one or moreprocessors; and determine that the output of the antenna does notsatisfy a threshold criteria.
 8. The electronic device of claim 7,wherein the one or more processors are further configured to determinean antenna load mismatch.
 9. The electronic device of claim 7, whereinthe one or more processors are further configured to determine animpedance mismatch.
 10. A method comprising: receiving, via atransceiver, a time instant reference from an other electronic device,wherein the time instant reference is used in processing Ultra Wideband(UWB) communications between the electronic device and the otherelectronic device; receiving, via the transceiver, a ranging signalbased at least in part on the time instant reference; and estimating adistance between the electronic device and the other electronic devicebased at least in part on the time instant reference and the rangingsignal.
 11. The method of claim 10, wherein the time instant referenceidentifies a center sample of a main lobe of the ranging signal.
 12. Themethod of claim 10, wherein the time instant reference identifies afirst sample of a main lobe of the ranging signal.
 13. The method ofclaim 10, wherein the time instant reference satisfies one or moreregional aspects associated with a location of the electronic device.14. The method of claim 10, further comprising: determining aperformance characteristic of a previously transmitted ranging signal;determining a different time instant reference; transmitting thedifferent time instant reference to the other electronic device; andtransmitting another ranging signal using the different time instantreference to the other electronic device.
 15. The method of claim 10,wherein estimating the distance comprises using the time instantreference to calculate a time-of-flight associated with the rangingsignal.
 16. A non-transitory computer-readable medium havinginstructions stored therein, which when executed by one or moreprocessors in an electronic device cause the one or more processors toperform operations for utilizing a pulse shaping interoperabilityprotocol for Ultra Wideband (UWB) communications, the operationscomprising: receiving, via a transceiver, a time instant reference froman other electronic device, wherein the time instant reference is usedto process Ultra Wideband (UWB) communications between the electronicdevice and the other electronic device, wherein the time instantreference satisfies one or more regional aspects associated with alocation of the electronic device; receiving, with the electronicdevice, a ranging signal based at least in part on the time instantreference; and computing a distance between the electronic device andthe other electronic device based at least in part on the time instantreference and the ranging signal.
 17. The non-transitorycomputer-readable medium of claim 16, wherein the time instant referenceidentifies a center sample of a main lobe of the ranging signal.
 18. Thenon-transitory computer-readable medium of claim 16, wherein the timeinstant reference identifies a first sample of a main lobe of theranging signal.
 19. The non-transitory computer-readable medium of claim16, wherein the operations further comprise: determining performancecharacteristics of a previously transmitted ranging signal; determininga different time instant reference; transmitting the different timeinstant reference to the other electronic device; and transmittinganother ranging signal using the different time instant reference to theother electronic device.
 20. The non-transitory computer-readable mediumof claim 16, wherein the determining the performance characteristicsoperation comprises: measuring an output of an antenna communicativelycoupled to the one or more processors; and determining that the outputof the antenna does not satisfy a threshold criteria.